docs: def load(self, instance, xblock):
          """
          Get the filesystem for the field specified in 'instance' and the
          xblock in 'xblock' It is locally scoped.
          """
  
          # TODO: Get xblock from context, once the plumbing is piped through
          if djpyfs:
              return djpyfs.get_filesystem(scope_key(instance, xblock))
          else:
              # The reference implementation relies on djpyfs
              # https://github.com/edx/django-pyfs
              # For Django runtimes, you may use this reference
              # implementation. Otherwise, you will need to
              # patch pyfilesystem yourself to implement get_url.
              raise NotImplementedError("djpyfs not available")